For projects that include external repos, it would be handy to insert the relative dependency paths ONLY when importing the necessary module.

Here is an example project layout:

Project root
+-- external repo/
      +-- lib/
           +-- config  # defines Config class
      +-- utils/
+-- mypackageA
     +-- __init__.py
     +-- app.py
main.py

In main.py, when an app instance that depends on the Config.py module in the external repo is created, the sys.path must include external repo/lib at the time of importing app:

from mypackageA import app
app.App()

Instead of setting the PYTHONPATH statically, an alternative is to modify sys.path in mypackageA.__init__.py by inserting paths to external repo/lib for the app module to import Config. However, vscode shows unresolved import warnings in this use case.